The invention relates to a parking brake. The invention relates in particular to an electrically actuable parking brake.
A parking brake is known from EP 0 729 871 A1, and corresponding U.S. Pat. No. 5,769,189 A1, in which a friction lining can be pressed against a brake disc by means of a brake piston. For this purpose pressurised hydraulic fluid is conventionally introduced into a hydraulic chamber in the case of service braking operations, of which chamber one limiting wall is formed by the brake piston. The pressure in the hydraulic chamber leads to displacement of the brake piston, and thus of the friction lining, in the direction of the brake disc. This known vehicle brake can be used as a parking brake, in addition to being used as a service brake. For this purpose it comprises an electrically actuable spindle/nut arrangement for mechanically securing the brake piston in a state in which the friction lining is engaged with the brake disc.
Brake arrangements are also known in which, instead of hydraulic actuation, an electrical drive brings about the displacement of the brake piston, and thus of the friction lining, in the direction of the brake disc and away from it (also) in the case of service braking operations. The electromechanical brake in DE 102 12 612 A1 for example dispenses completely with hydraulic transmission of the actuating force. A pedal force applied by the driver is detected and transmitted as an electrical signal to a controller. After evaluating various further sensor signals (for example operating parameters of the brake), the controller meters the braking force.
The current consumption of the electric motor is used as one of the measured quantities for adjustment of the application force in electrically actuable parking brakes. The size of the current consumption of the electric motor is designated as the cutoff current, at which size a desired application force is attained in the callipers. The electric motor is cut when this current is reached. A self-locking gearing or other means mean that the attained application force is maintained despite cutting of the electric motor.